The typical refrigeration display case is comprised of a cabinet having an interior display space for displaying comestibles which must be refrigerated to prevent spoilage or deterioration of quality or edibility. Typically, such refrigeration display cases are of two types. Both types generally include a means for refrigerating air in the interior display space while attempting to permit ready access and removal of those comestibles displayed.
The first type of refrigeration display cabinet typically includes an access opening covered by a movable door or similar member. This door generally includes a transparent portion comprised of one or more thermally insulating panes. This door prevents intermixing of environmental air found outside the refrigerated display case with the refrigerated air cooled inside the display space to minimize the warming effect of the environmental air upon the cooled air in the display space. However, as these refrigeration display cases are typically located in supermarkets and grocery stores where the door must be frequently opened, the effectiveness of the door in preventing air intermixing is somewhat limited. Furthermore, persons attempting to retrieve comestibles from the interior display space of the refrigeration cabinet are required to open and close the door member, which is often heavy and unwieldy. This design furthermore has the disadvantage of requiring a number of components which in turn increases the cost and maintenance of the unit.
The second typical refrigeration display case includes a cabinet having at least one wall with an access opening to an interior display space defined within the refrigeration cabinet. This access opening typically has at least one air curtain disposed across the access opening, flowing from an outlet in one side of the access opening to an inlet in the opposite side of the access opening. The air curtain is best defined as a strata of air of a given temperature and velocity bounded by air of relatively different temperature and velocity. The air curtain may range in thickness, for example, from 2 to 4 inches and in velocity from 2 to 13.5 feet per second. Due to the distance which must be traversed by the air curtain, it has been found that the air curtain often suffers from deterioration at its boundries due to the entrainment of environmental air. Further, the air curtain often entrains an undesirable amount of moisture from the environmental air, as the environmental air is typically at a higher temperature and thus contains a larger quantity of water vapor in an equal volume of air than found in the air of the air curtain. Also, the air curtain suffers increasing deterioration and moisture entrainment in proportion to the distance it must traverse.
In order to minimize this entrainment and deterioration effects, it is typical to provide multiple air curtains directed concurrently such that the strata of the respective air curtains are parallel, adjacent and flow in the same direction. This configuration permits the interior air curtains to entrain relatively less environmental air and moisture, as the exterior air curtain is primarily exposed only to environmental air and, therefore, is the primary air curtain entraining the excess moisture. The air in the air curtains then re-enters a conduit within the cabinet and passes through a refrigeration evaporator for cooling to the desired temperature.
A disadvantage of the crossflow air curtain method arises in that the air in the air curtain having entrained excess moisture then deposits the excess moisture upon the refrigeration evaporator. This increases the defrost requirement, thus increasing the heat injected into the refrigeration cabinet and the refrigeration workload with associated increase in cost and decrease in efficiency. This problem has been dealt with in various systems by providing multiple evaporators, or providing switchable air conduits within the cabinet for directing flow alternately through different refrigeration evaporators. Systems such as these have an increased number of components with increased maintenance requirements, cabinet costs and complexity of construction. None of these systems deal satisfactorily with the problem of providing a satisfactory minimum air curtain length while at the same time providing an access opening of the maximum width for ease of consumer access to the comestibles contained in the refrigeration compartment.
Therefore, in consideration of the foregoing, it is an object of the invention to provide an island-type refrigeration display cabinet having a single, multi-sectional air curtain to provide maximum access opening size in such a cabinet.
It is another object of the invention to provide an island type refrigeration display cabinet having an air curtain having a low velocity and extending a minimum distance across the access opening to entrain a minimal amount of moisture.
It is still a further object of the invention to provide such a cabinet having a simple air flow circuit.
It is yet another object of the invention to provide an island-type refrigeration cabinet of relatively simple, inexpensive construction.
It is yet another object of the invention to provide an island-type refrigeration display cabinet to provide in such a cabinet a simple means of defrosting the included refrigeration system.
It is another object of the invention to provide such a cabinet as is simple of operation and maintenance.
These and other objects of the invention will be apparent from the attached drawings and the description of the preferred embodiment that follows herein.